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<p align="center"><font face="book antiqua" size="6" color="#0000ff">bmp format</font></p>
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<table border="0" width="88%">
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<td width="100%"><b><p align="justify"><font face="book antiqua" size="6">table of
contents</font></p>
<font face="book antiqua" size="4"><p><a href="#_toc381201081">introduction</a> <br>
<a href="#_toc381201082">bitmap file format</a><br>
</font><font face="book antiqua" size="3">
<a
href="#_toc381201083">general</a> <br>
<a
href="#_toc381201084">bmp contents</a> <br>
</font><font face="book antiqua" size="4"><a href="#_toc381201085">field details </a><br>
</font><font face="book antiqua" size="3">
<a
href="#_toc381201086">height field </a><br>
<a
href="#_toc381201087">bits per pixel field</a> <br>
<a
href="#_toc381201088">compression field</a> <br>
<a
href="#_toc381201089">colors field</a> <br>
<a
href="#_toc381201090">important colors field</a> </font><u><font face="book antiqua"
size="4"></p>
</font></u><font face="book antiqua" size="6"><a name="_toc381201081"><p>introduction</a></p>
</font></b><font face="book antiqua" size="3"><p align="justify">this document describes
the microsoft windows and ibm os/2 picture bitmap files, called bitmaps or bmp files. most
of the descriptions of the bmp file concentrate on the microsoft windows bmp structures
like </font><font face="courier new" size="3">bmpinfoheader</font><font
face="book antiqua" size="3"> and </font><font face="courier new" size="3">bmpcoreinfo</font><font
face="book antiqua" size="3"> , but only a few describe the file contents on byte level.
this information is therefor only intended to be used in applications where direct reading
and writing of a bmp file is required.</p>
</font><b><font face="宋体" lang="zh-cn" size="6"><p align="justify"></font><font
face="book antiqua" size="6"><a name="_toc381201082">bitmap file format</a></p>
</font></b><font face="book antiqua" size="3"><p align="justify">the following chapters
contain the detailed information on the contents of the bmp file. first more general
information will be given regarding the byte order and file alignment. the second chapter
will concentrate on the byte-level contents of a bmp file. the third chapter will
elaborate on this chapter and explain some of the concepts - like compression - and/or
values in detail.</p>
</font><b><font face="宋体" lang="zh-cn" size="5"><p></font><font face="book antiqua"
size="5"><a name="_toc381201083">general</a></p>
</font></b><font face="book antiqua" size="3"><p align="justify">the bmp file has been
created by microsoft and ibm and is therefor very strictly bound to the architecture of
the main hardware platform that both companies support: the ibm compatible pc. this means
that all values stored in the bmp file are in the intel format, sometimes also called the
little endian format because of the byte order that an intel processor uses internally to
store values.</p>
<p align="justify">the bmp files are the way, windows stores bit mapped images. the bmp
image data is bit packed but every line must end on a dword boundary - if that</font><font
face="宋体" lang="zh-cn" size="3">抯</font><font size="3"> </font><font
face="book antiqua" size="3">not the case, it must be padded with zeroes. bmp files are
stored bottom-up, that means that the first scan line is the bottom line. </p>
<p align="justify">the bmp format has four incarnations, two under windows (new and old)
and two under os/2, all are described here.</p>
</font><b><font face="宋体" lang="zh-cn" size="5"><p></font><font face="book antiqua"
size="5"><a name="_toc381201084">bmp contents</a></p>
</font></b><font face="book antiqua" size="3"><p align="justify">the following table
contains a description of the contents of the bmp file. for every field, the file offset,
the length and the contents will be given. for a more detailed discussion, see the
following chapters.</p>
</font><table border="1" cellspacing="2" bordercolor="#000000" cellpadding="7" width="657">
<tr>
<td width="10%" valign="top"><font face="book antiqua" size="3" color="#808080"><b><p
align="justify">offset</b></font></td>
<td width="16%" valign="top"><font face="book antiqua" size="3" color="#808080"><b><p
align="justify">field</b></font></td>
<td width="14%" valign="top"><font face="book antiqua" size="3" color="#808080"><b><p
align="justify">size</b></font></td>
<td width="61%" valign="top"><font face="book antiqua" size="3" color="#808080"><b><p
align="justify">contents</b></font></td>
</tr>
<tr>
<td width="10%" valign="top"><font face="book antiqua" size="3"><p align="justify">0000h</font></td>
<td width="16%" valign="top"><font face="book antiqua" size="3"><p align="justify">identifier</font></td>
<td width="14%" valign="top"><font face="book antiqua" size="3"><p align="justify">2 bytes</font></td>
<td width="61%" valign="top"><font face="book antiqua" size="3"><p align="justify">the
characters identifying the bitmap. the following entries are possible:</p>
</font><font face="宋体" lang="zh-cn" size="3"><p align="justify">態</font><font
face="book antiqua" size="3">m</font><font size="3">’ </font><font face="book antiqua"
size="3">- windows 3.1x, 95, nt, </font><font size="3">…</font><font face="book antiqua"
size="3"></p>
</font><font face="宋体" lang="zh-cn" size="3"><p align="justify">態</font><font
face="book antiqua" size="3">a</font><font size="3">’ </font><font face="book antiqua"
size="3">- os/2 bitmap array</p>
</font><font face="宋体" lang="zh-cn" size="3"><p align="justify">慍</font><font
face="book antiqua" size="3">i</font><font size="3">’ </font><font face="book antiqua"
size="3">- os/2 color icon</p>
</font><font face="宋体" lang="zh-cn" size="3"><p align="justify">慍</font><font
face="book antiqua" size="3">p</font><font size="3">’ </font><font face="book antiqua"
size="3">- os/2 color pointer</p>
</font><font face="宋体" lang="zh-cn" size="3"><p align="justify">慖</font><font
face="book antiqua" size="3">c</font><font size="3">’ </font><font face="book antiqua"
size="3">- os/2 icon</p>
</font><font face="宋体" lang="zh-cn" size="3"><p align="justify">慞</font><font
face="book antiqua" size="3">t</font><font size="3">’ </font><font face="book antiqua"
size="3">- os/2 pointer</font></td>
</tr>
<tr>
<td width="10%" valign="top"><font face="book antiqua" size="3"><p align="justify">0002h</font></td>
<td width="16%" valign="top"><font face="book antiqua" size="3"><p align="justify">file
size</font></td>
<td width="14%" valign="top"><font face="book antiqua" size="3"><p align="justify">1 dword</font></td>
<td width="61%" valign="top"><font face="book antiqua" size="3"><p align="justify">complete
file size in bytes.</font></td>
</tr>
<tr>
<td width="10%" valign="top"><font face="book antiqua" size="3"><p align="justify">0006h</font></td>
<td width="16%" valign="top"><font face="book antiqua" size="3"><p align="justify">reserved</font></td>
<td width="14%" valign="top"><font face="book antiqua" size="3"><p align="justify">1 dword</font></td>
<td width="61%" valign="top"><font face="book antiqua" size="3"><p align="justify">reserved
for later use.</font></td>
</tr>
<tr>
<td width="10%" valign="top"><font face="book antiqua" size="3"><p align="justify">000ah</font></td>
<td width="16%" valign="top"><font face="book antiqua" size="3"><p align="justify">bitmap
data offset</font></td>
<td width="14%" valign="top"><font face="book antiqua" size="3"><p align="justify">1 dword</font></td>
<td width="61%" valign="top"><font face="book antiqua" size="3"><p align="justify">offset
from beginning of file to the beginning of the bitmap data.</font></td>
</tr>
<tr>
<td width="10%" valign="top"><font face="book antiqua" size="3"><p align="justify">000eh</font></td>
<td width="16%" valign="top"><font face="book antiqua" size="3"><p align="justify">bitmap
header size</font></td>
<td width="14%" valign="top"><font face="book antiqua" size="3"><p align="justify">1 dword</font></td>
<td width="61%" valign="top"><font face="book antiqua" size="3"><p align="justify">length
of the bitmap info header used to describe the bitmap colors, compression, </font><font
size="3">… </font><font face="book antiqua" size="3">the following sizes are possible:</p>
<p align="justify">28h - windows 3.1x, 95, nt, </font><font size="3">…</font><font
face="book antiqua" size="3"></p>
<p align="justify">0ch - os/2 1.x</p>
<p align="justify">f0h - os/2 2.x</font></td>
</tr>
<tr>
<td width="10%" valign="top"><font face="book antiqua" size="3"><p align="justify">0012h</font></td>
<td width="16%" valign="top"><font face="book antiqua" size="3"><p align="justify">width</font></td>
<td width="14%" valign="top"><font face="book antiqua" size="3"><p align="justify">1 dword</font></td>
<td width="61%" valign="top"><font face="book antiqua" size="3"><p align="justify">horizontal
width of bitmap in pixels.</font></td>
</tr>
<tr>
<td width="10%" valign="top"><font face="book antiqua" size="3"><p align="justify">0016h</font></td>
<td width="16%" valign="top"><font face="book antiqua" size="3"><p align="justify">height</font></td>
<td width="14%" valign="top"><font face="book antiqua" size="3"><p align="justify">1 dword</font></td>
<td width="61%" valign="top"><font face="book antiqua" size="3"><p align="justify">vertical
height of bitmap in pixels.</font></td>
</tr>
<tr>
<td width="10%" valign="top"><font face="book antiqua" size="3"><p align="justify">001ah</font></td>
<td width="16%" valign="top"><font face="book antiqua" size="3"><p align="justify">planes</font></td>
<td width="14%" valign="top"><font face="book antiqua" size="3"><p align="justify">1 word</font></td>
<td width="61%" valign="top"><font face="book antiqua" size="3"><p align="justify">number
of planes in this bitmap.</font></td>
</tr>
<tr>
<td width="10%" valign="top"><font face="book antiqua" size="3"><p align="justify">001ch</font></td>
<td width="16%" valign="top"><font face="book antiqua" size="3"><p align="justify">bits
per pixel</font></td>
<td width="14%" valign="top"><font face="book antiqua" size="3"><p align="justify">1 word</font></td>
<td width="61%" valign="top"><font face="book antiqua" size="3"><p align="justify">bits
per pixel used to store palette entry information. this also identifies in an indirect way
the number of possible colors. possible values are:</p>
<p align="justify">1 - monochrome bitmap</p>
<p align="justify">4 - 16 color bitmap</p>
<p align="justify">8 - 256 color bitmap</p>
<p align="justify">16 - 16bit (high color) bitmap</p>
<p align="justify">24 - 24bit (true color) bitmap</p>
<p align="justify">32 - 32bit (true color) bitmap</font></td>
</tr>
<tr>
<td width="10%" valign="top"><font face="book antiqua" size="3"><p align="justify">001eh</font></td>
<td width="16%" valign="top"><font face="book antiqua" size="3"><p align="justify">compression</font></td>
<td width="14%" valign="top"><font face="book antiqua" size="3"><p align="justify">1 dword</font></td>
<td width="61%" valign="top"><font face="book antiqua" size="3"><p align="justify">compression
specifications. the following values are possible:</p>
<p align="justify">0 - none (also identified by bi_rgb)</p>
<p align="justify">1 - rle 8-bit / pixel (also identified by bi_rle4)</p>
<p align="justify">2 - rle 4-bit / pixel (also identified by bi_rle8)</p>
<p align="justify">3 - bitfields (also identified by bi_bitfields)</font></td>
</tr>
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